1. Technical Field
The present invention relates to device-to-device (D2D) communication and more specifically to a method for setting synchronization between terminals in D2D communication based on a cellular communication system.
2. Related Art
Recently, ways of performing direct communication between devices in a cellular communication system have been under discussion. This is because there are requirements of network capacity, data transmission rate, good service quality etc. enabling provision of services to many people, according to rapid increase of data traffic due to spread of various communication terminals.
As a way of satisfying user requirements by enhancing an existing mobile communication network at a low cost, a direct communication between mobile communication devices, that is D2D (device-to-device) communication, has been considered.
A device is a communication terminal included in a cell, and serves the same function as user equipment (UE), but when direct communication is performed between two devices, it is called D2D communication.
The concept of D2D communication is used in fields such as sensor networks, WIFI direct etc., and recently discussions on D2D communication based on a cellular communication system in 3GPP system have also begun.
When D2D communication is performed based on the cellular communication system, there may be merits of wide coverage of a macro cell and resource reusability. Initiation of D2D communication is determined by a base station or a network and the base station or the network should inform the terminal of settings for the D2D communication. In this case, a procedure of setting synchronization between terminals for the D2D communication is needed. In conventional studies, there was no specific suggestion about D2D synchronization setting control.